Chang-Jian Li

The influence of alloy phases in the precursors on the selenization reaction mechanisms

As precursors are deposited in different sequences, the alloy phases of Cu–In or Cu–Ga are observed. This leads to different selenized results, which consist of either the single quaternary CIGS or the phase-separated CIS and CIGS mixture. According to the analysis of experimental results, it can be concluded that the alloy phases in the precursors have a significant impact on the reaction mechanism and path in the selenization process. It is the Cu–Ga alloy phase in the precursors that suppresses the rapid transformation of Cu–In to CuInSe2. Hence at 450 °C the Cu–Ga and Cu–In can react together with Se to form CIGS. With higher temperature annealing at 560 °C, the single quaternary CuIn0.7Ga0.3Se2 phase can be obtained.

Novel in situ resistance measurement for the investigation of CIGS growth in a selenization process

During the selenization process of CIGS thin films, the relation between the element loss rate and the precursor depositions are analyzed. The growth of the CIGS thin films during the selenization process is investigated by the novel in situ resistance measurement, by which the formation of compound semiconductors can be observed directly and simultaneously. Their structures, phase evolutions and element losses are analyzed by XRD and XRF. Based on the experimental results, it can be concluded that the phase transforms have nothing to do with the deposition sequences of precursors, while the element loss rates are related to the deposition sequences in this process. In addition, element loss mechanisms of CIGS thin films prepared by the selenization process are analyzed by the phase evolutions and chemical combined path in the In, Ga–Se reaction processes. Moreover it is verified that the element losses are depressed by increasing the ramping-up rate finally. The results provide effective methods to fabricate high-quality CIGS thin films with low element losses.